This application relates generally to disc drives for storing data and more particularly relates to an impaction filter that reduces the number of airborne particulates, while simultaneously reducing acoustic noise and mechanical vibrations within a disc drive housing.
Efforts to miniaturize disc drives have resulted in disc drive designs that permit greater data storage density. Recent disc drive designs increase storage density by adding more discs to a disc drive and by increasing the track density of each disc. However, as the storage density increases, the disc drive""s ability to position a read/write head above a particular track becomes more difficult and more critical.
One approach to increasing the ability of the disc drive to more accurately position the read/write head is to reduce internal and/or external mechanical vibrations that may affect the operation of the disc drive. Vibrations tend to cause the disc drive to incorrectly position the read/write head. When vibrations affect the positioning of the read/write head, remedial procedures must be taken to correct the positioning. Such measures cost precious seek time and can significantly reduce a disc drive""s efficiency. Various attempts have been made to reduce internal and external vibrations that may affect the performance of a disc drive. However, these approaches generally require the addition of parts into the disc drive housing, thus frustrating the goal of disc drive miniaturization.
Vibrations also cause acoustic noise that may be perceivable by a disc drive user or may cause interference with other equipment. It is well known that the mechanical vibrations that cause perceivable acoustic noise can be generated by the movement of the disc. These mechanical vibrations are known to couple across the gap between the discs and the disc drive housing, thereby enabling the mechanical vibrations to emanate from the disc drive housing as acoustic noise. Acoustic noise is another reason that disc drive designers endeavor to reduce mechanical vibrations within a disc drive.
The presence of particulates within the housing of a disc drive is a well-documented phenomenon. If the particulates reside on the surface of a disc or otherwise interfere with the operation of the disc drive read/write head, such particulates can adversely affect the reading and writing operations of a disc drive. Moreover, as a disc spins within the disc drive housing, the disc causes air to flow, generally in a radial pattern with the spin direction of the disc. One problem caused by airflow in the disc drive housing is the transportation of particulates within the housing that can cause damage to the disc or interfere with the operation of the read/write head. The airflow can cause particulates to swirl within the housing and to collect on the disc and between the read/write head and the disc surface.
One approach to reducing the presence of particulates in the disc drive housing is to place filters in strategic locations within the disc drive housing. Such filters reduce the number of airborne particulates by filtering the air and slightly restricting airflow into the portion of the housing in which the disc resides. Unfortunately, the presence of other parts, such as the actuator arm, create tangential (i.e., not radial) airflow currents in the housing. Strategically positioned filters can fail to reduce particulates transported in the tangential airflow caused by parts other than the disc. Moreover, most filtration devices are solely directed at particulate filtration and do not reduce acoustic noise or mechanical vibrations in the disc drive housing.
FIG. 1 depicts a disc drive 100 equipped with a conventional particulate filtration system. The disc drive 100 includes a base 102 to which various components of the disc drive 100 are mounted. A top cover (not shown) cooperates with the base 102 to form an internal, hermetically sealed environment for the disc drive in a conventional manner. The primary disc drive components include a spindle motor 146 that rotates one or more discs 108 at a high speed. A disc shroud 150 can be formed in the base 102, thereby providing space for the discs 108 and other disc drive components. The discs 108 can be one or more discs that are typically arranged in a vertically oriented disc pack. The vertical dimension of all of the discs in the disk pack is the disc pack height. Information is written to and read from tracks on the discs 108 through the use of an actuator assembly 110, which rotates during a seek operation about a bearing shaft assembly 144 positioned adjacent the discs 108. Mounted at the distal end of the actuator assembly 110 is a read/write head 118. During a seek operation, the track position of the heads 118 is controlled through the use of a voice coil motor 124.
A flex assembly 130 provides electrical connection paths for the actuator assembly 110 while allowing pivotal movement of the actuator assembly 110 during operation. The flex assembly includes a printed circuit board 132 to which head wires (not shown) are connected; the head wires being routed along the actuator assembly 110 to the heads 118. The printed circuit board 132 typically includes circuitry for controlling the write currents applied to the read/write head 118 during a write operation and a preamplifier for amplifying read signals generated by the read/write head 118 during a read operation. The flex assembly terminates at a flex bracket 134 for communication through the base deck 102 to a disc drive control circuit board (not shown) mounted to the bottom side of the disc drive 100. The drive control circuit provides a communication interface between the disc drive 100 and a host device (not shown), such as a personal computer. For example, the personal computer may request information that is contained on the disc or may send information to be stored on the disc.
The disc 108, typically spins in the direction of arrow A. When the disc 108 rotates, airflow is generated by the rotation. Most of the airflow follows the radial direction of the disc and flows in the direction of arrows B and C. However, when the actuator arm 110 is extended toward the spindle motor 146, a negative pressure can be created by the airflow and a tangential airflow can be created, for example, in the direction of arrow D. It is well known that particulates can exist within the disc drive housing. Particulates can be dust, lubrication, or any other unfixed matter that may be present in the disc drive housing. Such particulates can cause damage to the disc 108, to the read/write head 118, and generally adversely affect the operation of the disc drive 100.
The disc drive 100 of FIG. 1 is equipped with two, conventional filtration devices 136, 140. A fence filter 136 has a filter element 138 that is positioned substantially perpendicular to the flat surface of the disc 108. The fence filter 136 is designed to catch particulates transported by radial airflow at the periphery of the disc 108. The fence filter 136 also can catch particulates transported by tangential airflow at the periphery of the disc 108, such as particulates carried in the direction of arrow D. However, the fence filter 136 is confined to a particular area of the disc drive housing and cannot collect particulates in radial or tangential airflow in other areas of the disc drive housing. A circulation filter 140 has a filter element 142 that is also positioned substantially perpendicular to the flat surface of the disc 108. The circulation filter 140 is designed to catch particulates transported by radial airflow at the periphery of the disc 108. The circulation filter 140 is incapable of catching particulates transported by tangential airflow at the periphery of the disc 108. Moreover, the circulation filter 140 is confined to a particular area of the disc drive housing and cannot collect particulates in radial airflow in other areas of the disc drive housing.
Therefore, there is a need in the art for a particulate filter that reduces particulates in circular, radial, and tangential airflow currents. The particulate filter should also function to reduce mechanical vibrations and acoustic noise in the disc drive.
Against this backdrop, embodiments of the present invention have been developed. An embodiment of the present invention incorporates the functionality of a particulate filter with that of an acoustic noise filter and a mechanical vibration filter. An impaction filter covers a selected portion of the surface area of the interior of the disc drive housing. The impaction filter is placed in an area of the disc drive housing in which the particulates will most likely be moving, thereby maximizing the probability of trapping the particulates. The position of the impaction filter with respect to the disc drive housing reduces particulates in both radial and tangential airflow currents. The impaction filter is constructed of a soft material, such as a mixed polypropylene and modified acrylic fibers, so that particulates are bound to the surface of the impaction filter upon impact. The textured surface of the filter and the static caused by the operation of the disc drive in close proximity with the filter cause the particulates to tend to remain bound to the filter. Because of the location of the impaction filter within the interior of the disc drive housing, the particulates in the tangential airflow currents are reduced. Moreover, the fabrication and location of the impaction filter reduces acoustic noise and mechanical vibrations.
In one embodiment of the present invention, a filtration system is provided for a disc drive that includes an elongate perimeter filter constructed of an electrostatic filter damping material. The elongate perimeter filter extends along a portion of an outer perimeter of a disc between the disc and the housing of the disc drive. The damping material has a textured surface for collecting particulates that impact the textured surface. The damping material is further operative to dampen mechanical energy by reducing the coupling of mechanical energy across the gap between the disc and the disc drive housing.
In another embodiment, a filtration system is provided for a disc drive that includes an arcuate cap filter constructed of a damping material. The arcuate cap filter extends along a portion of a top surface of a disc in proximity to the outer-most edge of the disc. The damping material has a textured surface for collecting particulates that impact the textured surface. The damping material comprises polypropylene and acrylic fibers and is operative to dampen mechanical energy passing through the damping material.
In yet another embodiment of the present invention, a disc drive boundary is provided. The disc drive boundary encloses at least a portion of an outside diameter of a rotating disc pack. The disc drive boundary includes an elongate filter that is fabricated of a damping material. The elongate filter has an inner surface that is textured and is positioned in close proximity to the outside diameter of the rotating disc pack. The damping material is made of polypropylene and acrylic fibers and is operative to collect particulates and to absorb mechanical energy. The elongate filter has a height that is substantially equal to a height of the disc pack.
These and various other features as well as advantages which characterize the present invention will be apparent from a reading of the following detailed description and a review of the associated drawings.